"I am in my early 60s. Have had chronic constipation ever since childhood (2 BMs per week), but it became much worse in the last couple of years (up to 2 weeks without BM). After more than a year of trying to find the optimal amount of Miralax to take per day per GI doctor's instructions, and when to also include stool softeners, I  was doing okay (BM every 4 or 5 days), but had occasional leakage. I started Amitiza two weeks ago at my internist's suggestion, two 8mg pills twice a day. It was like a miracle the first week - small to medium daily movements and a couple of large ones. No side effects. But now it stopped working. It has been 7 days with no BM. The last 2 days I took 24 mg. Also ate prunes and took stool softeners. Nothing yet."